WASHINGTON - President Barack Obama took aim Saturday at Republican senators standing in the way of a nuclear arms reduction pact with Russia, saying they were abandoning Ronald Reagan's lesson of nuclear diplomacy: "Trust but verify."

The Senate's GOP leader accused his Democratic counterparts of wasting Congress' lame-duck session on issues from gays in the military to environment regulations. Sen. Mitch McConnell, R-Ky., didn't mention Obama's push to ratify the new START weapons treaty with Russia, but said extending expiring Bush-era tax cuts needed to be the top priority.

Obama, speaking from a NATO summit in Portugal, used his weekly radio and Internet address to focus on international affairs at a time of increased political gridlock at home as the GOP prepares to take control of the House in the new Congress next year.

Describing his nuclear efforts as part of a five-administration continuum, Obama said the treaty to cut the permitted number of U.S. and Russian long-range nuclear warheads by a third was "fundamental to America's national security."

The president went to great length listing the prominent Republicans from previous administrations who back the deal, including former secretaries of state Colin Powell, George Shultz, Jim Baker and Henry Kissinger. He cited GOP Sen. Dick Lugar's support, but suggested that other Republican senators were playing politics with national security.

"Some make no argument against the treaty - they just ask for more time," Obama said. "If the Senate doesn't act this year - after six months, 18 hearings, and nearly a thousand questions answered - it would have to start over from scratch in January."

And it would face tougher odds as the Democratic majority loses six seats.

Without ratification, Russia may be less cooperative in enforcing strong sanctions on Iran, securing loose nuclear material from terrorists or helping the U.S. equip troops in Afghanistan, Obama said. He said no agreement with Russia meant no U.S. inspectors watching over one of the world's biggest nuclear arsenals.

"Those who would block this treaty are breaking President Reagan's rule - they want to trust, but not verify," Obama said.

At the NATO meeting, officials from Denmark, Lithuania, Latvia, Hungary, Norway and Bulgaria told reporters Saturday that failing to ratify the treaty would set back European security.

McConnell, in the GOP radio and Internet address, focused on the stubbornly high unemployment rate and Democrats' failure to alleviate joblessness. He said Democrats had exploded the national debt with the stimulus and other spending programs, and were now asking Americans for more money. He said it was imperative that the Bush-era tax cuts that expire this year be extended.

"Americans don't think we should be raising taxes on anybody, especially in the middle of a recession," McConnell said. "But instead of giving Americans what they want, Democratic leaders plan to use the last few days that lawmakers expect to spend in Washington this year focusing on everything except preventing this tax hike, which will cost us even more jobs: immigration; a repeal of the 'don't ask, don't tell'; a reorganization of the FDA; more environmental regulations."

Obama appears ready to compromise with Republicans on temporarily extending the tax cuts passed under President George W. Bush, despite previous opposition to continuing them for couples making over $250,000. Republicans have sought permanent cuts for all, and McConnell said that the blame for inaction would fall on the Democrats when the hikes "hit every taxpayer and hundreds of thousands of small businesses at the stroke of midnight on December 31st."

Still, he suggested that Republicans could compromise on the tax issue.